On the Implementation of Variable Speed in Pump-Turbine Units Providing Primary and Secondary Load-Frequency Control in Generating Mode

Abstract

This paper analyses different control strategies for the speed control loop of a variable-speed pump-turbine unit equipped with a doubly fed induction generator, operating in generating mode in an isolated power system with high penetration of intermittent renewable energy. The control strategies are evaluated and compared to each other in terms of the amount of water discharged through the pump-turbine and of the wicket gates fatigue while providing primary and secondary load-frequency control. The influence of the penstock length and the initial operating point on the performance of each control strategy is studied in detail. For these purposes, several simulations have been performed with a suitable dynamic model of the pumped-storage hydropower plant and the power system. The results of the paper indicate that a proper control strategy would consist in updating the reference speed according to the power generation schedule and keeping it constant within each scheduling period (typically 1 h).

Nonlinear Modeling and Stability of a Doubly-Fed Variable Speed Pumped Storage Power Station with Surge Tank Considering Nonlinear Pump Turbine Characteristics

“…Therefore, the stator resistance of the motor can be ignored. By substituting R s = 0 and Equation (13) into Equations ( 4)- (5) we yield [16]:…”

“…The different control strategies for VSPSPS connected to an isolated power system with high penetration of intermittent renewable energy were studied. The effect mechanism of penstock length and initial operating point on the dynamic performance was then investigated [13].…”

Cooperative control strategy for frequency regulation of wind-pumped storage system considering wind speed partition

“…As a new form of energy storage that has been vigorously developed in recent years, pumped storage has received attention because of its large storage capacity, low operating cost, and long cycle life (Zhao et al, 2023), in which VSPS with doubly-fed induction machine is a hot spot for current research due to the advantages of flexible and adjustable unit speed and the hydraulic characteristics of the prime mover that do not directly affect the output power, etc. Currently, research on the application of VSPS to PFR has been conducted (Chen et al, 2023; Li et al, 2023; Sarasúa et al, 2015; Xu et al, 2023). However, the focus of the existing research is mainly on the modeling, frequency regulation performance evaluation and the design of the frequency control link of the doubly-fed pumped storage unit itself, while in fact, the VSPS can be used to improve the frequency regulation capability of the DFWT by forming a joint system with the DFWT under the power-first control mode, so that the wind-pumped storage system has the overall frequency response characteristics similar to that of SG.…”

The Strategy of Considering the Participation of Doubly-Fed Pumped-Storage Units in Power Grid Frequency Regulation

“…Compared with the traditional power grid, in which only the TPU participates in the system frequency regulation [8][9][10], the DFPSU participates in the grid frequency regulation, which has the advantage of automatically tracking the grid frequency changes, and can quickly smooth the grid frequency fluctuations in a short time, and adjust the frequency of the grid. The method is more flexible, the storage capacity is larger, and the environmental pollution is smaller [11,12]. Therefore, in the future, the strategy research on the participation of the DFPSU in power grid frequency regulation will receive more and more attention.…”